Photoconductive pickup tube with unitized electrode structure having the photoconductive target electrode spaced from the tube faceplate

ABSTRACT

A photoconductive pickup tube utilizes a one-piece envelope, with a closed-end faceplate portion, wherein a unitized mount structure is positioned. The integrated mount includes a beam forming portion with a mesh electrode oriented relative to the frontal end thereof. The unitized array continues whereof a target substrate, having a photoconductive target electrode formed thereon, is insulatively spaced from the mesh electrode. Resilient means are terminally employed to space the target substrate from the interior surface of the envelope faceplate, and a connective means for the target electrode is extended in an insulated manner along the mount to emerge from the base portion of the envelope.

United fitates Fate [72] Inventors JohnJ.Miller 5/1966 Shallcross 313/65A lv=: w I N 3,256,455 6/l966 Saldi 313/65 A at enlrd, ater 00, both of.Y. Pri Examiner Roy Lake [21] Appl. No. 11,616 3 Assistant Exammer-V.Lafranchi [22] Filed Feb. 16,1970 A l D d C [45] Patented Nov. 9, 1971lt0rneys -Norman J. Mal ey, onal R. astle and Frederick H. Rinn [54]PHOTOCONDUCTIVE PICKUP TUBE WITH UNITIZED ELECTRODE STRUCTURE HAVING THEPHOTOCONDUCTIV E TARGET ELECTRODE SPACE!) FROM THE TUBE FACEPLATE 9Claims 5 Drawing Figs. A BSTRACT: A photoconductive pickup tube utilizesa onepiece envelope, with a closed-end faceplate portion, wherein a [52]US. Cl 313/65 A, iti d mount Structure i iti d Th i t t d mount 313/268,313/269, 31.3/285 includes a beam forming portion with a mesh electrode[5 l 1 Int. T. oriented relative to the frontal end thereof The uniflzgdarray 1/92, 19/46, 31/26 continues whereof a target substrate, having aphotoconduc- Fleld of Search five tar et electrode formed thereon isinsulatiyely spaced 65 65 282, 234, 285, 268 from the mesh electrode.Resilient means are terminally employed to space the target substratefrom the interior surface [56] References cued of the envelopefaceplate, and a connective means for the tar- UNITED STATES PATENTS getelectrode is extended in an insulated manner along the 3,202,857 8/1965Antoniades 313 /65 A mount to emerge from the base portion of theenvelope 17' l 4 2 f l 3 3 2 a /V I I/r 3 3 47 4- m/ 6| 5 1 '1 32 39 l27 114mm II 65 r '1 26 65 '-l i I l 65 l I I I5 PATENTEU 9 3,6193 8 5SHEET 1 OF 2 INVENTORS. JOHN J. MILLER 8. By CARL W. PENIRD jD O E-ATTORNEY PATENTEDuuv 9 I97] SHEET 2 BF 2 INVENTORS. JOHN J.M|LLER 8.

CARL W. PENIRD ATTORNEY PHOTOCONDUCTIVE PICKUP TUBE WITH UN ITIZEDELECTRODE STRUCTURE HAVING THE PHOTOCONDUCTIVE TARGET ELECTRODE SPACEDFROM THE TUBE FACEPLATE BACKGROUND OF THE INVENTION This inventionrelates to cathode-ray tubes and more particularly to a photoconductivepickup tube of the type utilized in television camera applications and amethod of fabricating the same.

Many of the photoconductive tubes conventionally utilized in televisionapplications are normally relatively complicated structures, and as suchare not readily conducive to expeditious methods of fabrication. It wasfound extremely difficult to consistently form photoconductive targetelectrodes on the face areas of closed end tubes and make satisfactoryelectrical connections thereto. In view of this difficulty, it has beencommon practice to construct pickup tubes having the photoconductivetarget electrode disposed on the inner surface of a separate glassfaceplate which is then usually indium-sealed to an open envelopeportion. It has been conventional practice to utilize the indium seal asa means for effecting an external connection for the target electrode.Such seals were found to be expensive, first, in view of the cost of theindium material seal, and second, because of the special treatment thatmust be given the glass to insure hennetic tightness.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention toreduce the aforementioned disadvantages and to provide a photoconductivepickup tube of a structure that can be expeditiously and inexpensivelyfabricated.

Another object is to provide a pickup tube wherein the target electrodeis not directly associated with the faceplate of the tube.

A further object is to provide a method of fabricating a pickup tube byconsidering the internal tube structure as a wholly separateconstruction.

The foregoing objects are achieved in one aspect of the invention byproviding a pickup tube employing a one-piece envelope having a closedend faceplate wherein a stacked array of related elements is positionedas a unitized mount structure. The integrated array in the unitizedmount includes a basic multielectrode beam forming structure, upon whicha mesh electrode is oriented relative to the frontal open end thereof.Spaced from the mesh electrode, by insulative spacer means, is atransparent target substrate having a photoconductive target electrodeformed on the rear surface facing the mesh electrode. Relative to thefront surface of the target substrate are terminal spacing meansperipherally and longitudinally oriented to provide resilient spacingbetween the target substrate and the interior surface of the envelopefaceplate. Target electrode connective means are extended longitudinallyin an insulated manner along the mount structure to emerge from baseportion of the envelope. The aforedescribed photoconductive pickup tubeutilizing the unitized mount construction and one-piece envelopeconcepts can be expeditiously and economically fabricated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional viewshowing a photoconductive tube incorporating the concepts of theinvention;

FIG. 2 is an enlarged cross section of the forward portion of the tubedetailing aspects of the invention as viewed relative to the line 2-2 ofFIG. 3;

FIG. 3 is a plan view showing the end of the mount structure taken alongthe line 3-3 of FIG. 2;

FIG. 4 is an enlarged cross section of the forward portion of the tubeillustrating another embodiment of the invention; and

F IG. 5 is a perspective illustrating an alternate embodiment of theterminal spacing means.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding ofthe present invention, together with other and further objects,advantages and capabilities thereof, reference is made to the followingspecification and appended claims in connection with the aforedescribeddrawings.

The term one-piece envelope" as used herein is intended to include abulb structure wherein the closed end or faceplate portion is:

l. a continuation of the same glass comprising the envelope sidewall; or

2. of different glass than that of the envelope sidewall but expansivelycompatible therewith.

With reference to the drawings, there is shown in FIG. 1 aphotoconductive pickup tube 11 having a one-piece evacuated envelope 13which comprises a wall portion 15, an integral closed end faceplateportion 17, and an opposed base closure portion 19. Positioned thereinis a unitized internal mount construction 21 which is supported by thebase portion 19 and comprises a multielectrode electron beam formingstructure of which only a substantially tubular control electrode 23 isshown. A plurality of electrical connective means 22 are arranged toextend exteriorly from the internal mount structure 21 through the baseportion 19. A substantially planar mesh electrode 25 is supportedrelative to and parallel with the open frontal end of the controlelectrode 23. Spaced from the mesh electrode 25, by spacer means 27, isa substantially transparent planar target substrate 29 which issupported by an annular support means 33. A photoconductive signal ortarget electrode 41 is suitably formed on the rear surface of thesubstrate 29 facing the mesh electrode 25. An electrical connection 45for the target electrode 41 is formed and disposed to extendlongitudinally in an insulated manner along the mount structure 21, inthe space between the control electrode 23 and the envelope wall portion15, to emerge from the base portion 19 as an external connection 45'.Extending longitudinally beyond the target substrate 29 are terminalspacing means 49 which are disposed in a peripheral manner to providesubstantially resilient spacing between the target substrate and theinterior surface of the envelope faceplate 17. A longitudinal axis 55extends through the one-piece envelope l3 and the encompassed internalunitized mount structure 21. At least three resilient spaced-apartpositioners 56 are employed to effect lateral support and positioning ofthe mount structure 21 within the envelope 13.

In operation, light rays 57 from external imagery are focused on thephotoconductive target electrode 41 by camera lens means 59. In thepickup tube 11 of this invention, the light rays 57', that have passedthrough the lens 59, are directed to traverse the tube faceplate portion17 in an unfocused condition. As such, the optical quality of the glasscomprising at least the central portion 17' of the faceplate 17 shouldbe substantially free of optical distortion but need not be as criticalas the quality of the glass of the target substrate 29 which iscontiguous to the plane of focus on the target electrode 41. Utilizationof the foregoing optical considerations plus the orientation of thetarget electrode connection through the base portion makes the one-pieceenvelope concept a feasible and advantageous construction.

With reference to FIGS. 1, 2, and 3, the structure and fabrication ofone embodiment of the pickup tube 11 of the invention will be describedin greater detail.

The substantially transparent planar target substrate 29 is ofdistortion free glass, such as one of the clear borosilieates, havingsmooth front and rear surfaces, 30 and 31 respectively. On the rearsurface 31, a substantially uniform and transparent electricallyconductive coating 32 is formed in a conventional manner, such as byheating the substrate and spraying substantially the whole of the rearsurface 31 with stannic chloride to form conductive tin oxide. Theconductively coated substrate 29 is then positioned in the femalesection 35 of the substrate annular support means 33 in a manner thatthe electrically conductive coating 32 makes contact with an instandingledge or shelf 37 of the female support section 35. With the substrateso positioned, a photoconductive material 39, such as for exampleantimony trisulfide, is suitably vaporized over the exposed coating oftin oxide 32 to form the target electrode 41. A metallic male section 42of the annular support means 33, having resilient terminal spacing means49 positioned and attached thereto, is then inserted into the femalesupport section 35 to substantially peripherally seat upon the uncoatedfront surface of the substrate. The male section 42 has a peripheralwall 43 which makes engagement with the peripheral wall 36 of the femalesection 35. The two sections and 42 of the annular support means 33 arethen bonded together such as by welding the peripheral wall 36 to thewall 43 to form an electrically conductive and supported targetelectrode structure 47.

The mesh electrode 25 is a planar foraminous screen which, dependingupon the resolution desired in the tube, may have from 500 to 1,000apertures per inch. This mesh screen is supported by a flanged supportring 26 which, as shown in FIG. 2, is positioned on and bonded to theopen frontal end of the control electrode 23 of the electron beamforming structure.

Target spacer means 27, in the form of an insulative ringcircumferentially dimensioned to have an opening at least substantiallyequaling the functional area of the mesh electrode 25, is peripherallypositioned between the mesh electrode 25 and the target or signalelectrode structure 47 to provide a stacked array of cooperatingelements. it has been found that the target spacer 27 can be suitablyformed from ceramic or glass. A target electrode connective lead 45 isterminally formed to facilitate bonding attachment to the targetelectrode structure 47 in a manner to function as both an electricalconnection and support means therefor. The connective lead 45 extendsalong the control electrode 23 encased in an insulator or standoff 24which is attached to the mount structure by clamping means 65. At leastone target electrode structure support 61, spaced from the connectivelead 45, is also bonded to the target electrode structure 47. As shownin FIGS. 2 and 3, three of such structure supports 61 are insulativel'yattached to the exterior wall of the control electrode 23 by insulators63 and welded clamping means 65. Thus, by the bonded electrodeconnective lead 45 and one or more of the structure supports 61, astacked unitized mount structure 21 is provided.

Reference is again made to the terminal spacing means 49. As shown inFIGS. 2 and 3, three substantially S-shaped resilient metallic elementsor snubbers, referenced as 49, are spacedly positioned and bonded to aninstanding ledge or shelf 51 of the male support section 42. Thesesnubbers 49 are formed to extend beyond the target electrode structure47 in a manner to contact the periphery of the envelope faceplateportion 17. The S-shaped resilient elements are not to be consideredlimiting as other configurations can function in a similar manner. Forexample, a metailic wiggle-washer 49 as shown in FIG. 5, is verticallyformed to seat on the instanding ledge 51 and provide the requiredterminal resilient spacing. This washer 49 may or may not be bonded tothe ledge 51 and is circumferentially dimensioned to have an opening atleast substantially equaling the functional area of the targetphotoconductive material 39.

Another embodiment of the forward end of the unitized mount structure 21is shown in FIG. 4 wherein the mesh electrode 25' is electricallyisolated from both the control electrode 23 and the target electrode 41.In certain types of pickup tubes such isolation is desired. This isaccomplished by positioning the mesh electrode 25 between theaforedescribed annular target spacer means 27 and a control electrodeannuiar insulative spacer 71, which is formed in a manner similar totarget spacer means 27 and seated on the open end of the beam controlelectrode 23. The insulated mesh electrode 25 may have a separateelectrical connection 73 attached thereto and formed to extendlongitudinally, encased in an insulator 75 attached to the controlelectrode 23, within the envelope in a manner to emerge outwardlythrough the base portion 19.

As in the first embodiment, the second embodiment is likewise supportedand unitized by the target electrode connective lead 45' and at leasttwo target electrode structure supports 61.

Upon being unitized, either mount structure is then inserted within theone-piece glass envelope in a manner that the resilient terminal spacingmeans 49, 49' makes seated peripheral engagement with the inner surfaceof the closed end faceplate portion 17. It has been found that a clearsoft lime glass is satisfactory material for the one-piece envelopeconstruction.

White the terminal spacing means 49 of the unitized amount structure 21are maintained in resilient engagement with the faceplate portion 17,base closure portion 19 is joined to the envelope 13 as by aconventional drop-seal technique to provide a glass enclosed structure.Subsequent gas evacuation, hermetic sealing, and tube processing of theglass enclosed structure provides the completed photoconductive pickuptube 11.

It is within the scope of the invention to rearrange certain of thefabrication steps as may be deemed conducive to efficient manufacturingprocedure.

Thus, a pickup tube structure is provided that can be expeditiously andinexpensively fabricated. By utilizing unitized mount construction,separate faceplate seals are eliminated, and all electrical connectionsare feasibly effected through the base. By removing the target electrodefrom the faceplate, the optical quality of the faceplate is lesscritical to the application. Therefore, less expensive envelopes areemployed, and the number of fabrication steps are reduced.

While there has been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention as defined bythe appended claims.

We claim:

1. A photoconductive pickup tube formed of a glass envelope having awall portion, a closed end faceplate portion of similar material and anopposed base closure portion providing a hermetic enclosure having alongitudinal axis wherein the internal tube construction is a stackedunit comprising:

a multielectrode beam forming structure having an extendingsubstantially tubular control electrode with a mesh electrode membersupported relative to and parallel with the open frontal end of saidtubular control electrode, said multielectrode beam forming structurehaving an axis substantially coincidental with said longitudinal axis ofsaid envelope;

a substantially transparent planar target substrate having front andrear surfaces positioned within said glass envelope in a manner spacedfrom said faceplate and adjacent to said mesh electrode;

a photoconductive target electrode disposed on the rear surface of saidsubstrate facing said mesh electrode;

a target connection for said photoconductive target electrode formed toextend longitudinally in an insulative manner within said envelope;

target spacer means positioned between said mesh electrode and saidtarget substrate;

provisions for Supporting said target substrate relative to said controlelectrode;

terminal spacing means extending longitudinally beyond said substrateand peripheraily contiguous thereto in a manner to provide substantiallyresilient spacing between said substrate and the interior surface ofsaid envelope faceplate, and

a plurality of electrical connective means including said targetconnection arranged to extend from said internal tube structure throughthe base portion of said envelope.

2. A photoconductive pickup tube according to claim 1 wherein saidtarget connection is formed as an insulated lead oriented in the spacebetween said control electrode and said envelope wall portion in amanner to extend therealong from said target to said base portion.

3. A photoconductive pickup tube according to claim 1 wherein saidtarget spacer is in the form of an insulative ring circumferentiallydimensioned to have an opening at least substantially equaling thefunctional area of said mesh electrode.

4. A photoconductive pickup tube according to claim 3 wherein saidtarget spacer is formed of glass.

5. A photoconductive pickup tube according to claim 1 wherein saidterminal spacing means is in the fonn of a resilient ringcircumferentially dimensioned to have an opening at least substantiallyequaling the functional area of said target photoconductive material.

6. A photoconductive pickup tube according to claim 1 wherein saidterminal spacing means is in the form of at least three spaced-apartsubstantially resilient snubbers extending beyond said target substratein a manner to contact the periphery of said envelope faceplate portion.

7. A photoconductive pickup tube according to claim 1 wherein the glassenvelope is of soft glass material whereof at least the central area ofthe closed end portion is substantially free of optical distortion.

8. A photoconductive pickup tube according to claim 1 wherein said meshelectrode is insulated from said tubular control electrode.

9. A photoconductive pickup tube according to claim 8 wherein saidinsulated mesh electrode has a separate electrical connection formed toextend longitudinally within said envelope and through said baseportion.

1. A photoconductive pickup tube formed of a glass envelope having awall portion, a closed end faceplate portion of similar material and anopposed base closure portion providing a hermetic enclosure having alongitudinal axis wherein the internal tube construction is a stackedunit comprising: a multielectrode beam forming structure having anextending substantially tubular control electrode with a mesh electrodemember supported relative to and parallel with the open frontal end ofsaId tubular control electrode, said multielectrode beam formingstructure having an axis substantially coincidental with saidlongitudinal axis of said envelope; a substantially transparent planartarget substrate having front and rear surfaces positioned within saidglass envelope in a manner spaced from said faceplate and adjacent tosaid mesh electrode; a photoconductive target electrode disposed on therear surface of said substrate facing said mesh electrode; a targetconnection for said photoconductive target electrode formed to extendlongitudinally in an insulative manner within said envelope; targetspacer means positioned between said mesh electrode and said targetsubstrate; provisions for supporting said target substrate relative tosaid control electrode; terminal spacing means extending longitudinallybeyond said substrate and peripherally contiguous thereto in a manner toprovide substantially resilient spacing between said substrate and theinterior surface of said envelope faceplate, and a plurality ofelectrical connective means including said target connection arranged toextend from said internal tube structure through the base portion ofsaid envelope.
 2. A photoconductive pickup tube according to claim 1wherein said target connection is formed as an insulated lead orientedin the space between said control electrode and said envelope wallportion in a manner to extend therealong from said target to said baseportion.
 3. A photoconductive pickup tube according to claim 1 whereinsaid target spacer is in the form of an insulative ringcircumferentially dimensioned to have an opening at least substantiallyequaling the functional area of said mesh electrode.
 4. Aphotoconductive pickup tube according to claim 3 wherein said targetspacer is formed of glass.
 5. A photoconductive pickup tube according toclaim 1 wherein said terminal spacing means is in the form of aresilient ring circumferentially dimensioned to have an opening at leastsubstantially equalling the functional area of said targetphotoconductive material.
 6. A photoconductive pickup tube according toclaim 1 wherein said terminal spacing means is in the form of at leastthree spaced-apart substantially resilient snubbers extending beyondsaid target substrate in a manner to contact the periphery of saidenvelope faceplate portion.
 7. A photoconductive pickup tube accordingto claim 1 wherein the glass envelope is of soft glass material whereofat least the central area of the closed end portion is substantiallyfree of optical distortion.
 8. A photoconductive pickup tube accordingto claim 1 wherein said mesh electrode is insulated from said tubularcontrol electrode.
 9. A photoconductive pickup tube according to claim 8wherein said insulated mesh electrode has a separate electricalconnection formed to extend longitudinally within said envelope andthrough said base portion.